This invention relates to a mold design for casting metal ingots, and in particular for casting aluminum ingot sows which are virtually cavity free, and to method of casting such sows.
A recurring problem in, for example, the remelting of aluminum sows is molten metal explosions. These explosions occur because of the internal cavities (shrinkage cavities) produced in the sows during their production, which production, for the most part, utilizes a warm mold, i.e., a mold that is used to cast several sows without allowing it to cool between casts.
These cavities are produced by the uneven heat dissipation from the mold during the production of the ingot producing voids in the body of the ingot within which moisture may accumulate. Sows containing these cavities represent a serious hazard for personnel and equipment in a cast shop. This is because the moisture accumulated in the cavities can create an explosion hazard when the sow is charged into molten metal in a furnace, for example, a remelt furnace.
If the remelt sow does not contain internal cavities, indoor storage in a heated building is sufficient to remove any surface moisture that accumulates. However, if the remelt sow contains internal cavities and has been exposed to outdoor storage, nothing short of furnace drying will eliminate the potential for serious explosions should the remelt sow be immersed in molten aluminum.
Although furnace drying is an expensive proposition, the risk associated with charging a remelt sow into molten aluminum when water is entrapped in the interior is unacceptable.
It would, therefore, be desirable to have some means of improving the state of cast metal ingots so that the noted internal cavities are minimized if not eliminated, and to achieve this state during the formation of the ingots.